Referring to FIG. 4, there is illustrated a prior art apparatus for performing electron beam duplication lithography using a photo cathode. A quartz substrate 41 forms the base of a mask plate 40 on which a chromium (Cr) light shield pattern 42 is formed. On the surface of substrate 41 and between the portions of the Cr light shield pattern 42, a photo cathode film 43 is deposited in a defined pattern. The photo cathode material 43 emits electrons when bombarded by light energy, such as ultra violet light 46. An exemplary photo cathode material is cesium iodide (CsI), which is a low work function material. An ultra violet light source (not shown) irradiates ultra violet light 46 through the backside of quartz substrate 41, bombarding the photo cathode film 43, resulting in a secondary emission of electrons 47 from the photo cathode patterned film 43. The emitted photo electrons 47 are accelerated by an electric field applied by acceleration electric source E, and may be focused into an electron beam 47 by a focusing magnetic field. (magnetic field lens) 48 created by magnetic coils (not shown), onto electron beam resist film 45 deposited on substrate plate 44. In this manner, the “lithography” is not created by light but by exposure of the resist film 45 to an electron beam The result is that the pattern formed by light shield pattern 42 and photo cathode film 43 is duplicated when portions of resist film 45 are bombarded by the electron beams 47. The electron beams change the molecular structure of the resist such that the portion of the resist bombarded by electrons is easy to dissolve in specific chemicals for the resist (“developer” chemicals).
However, there are several disadvantages to the prior art technique illustrated in FIG. 4. Because the mask plate is itself a passive light emission device using a photo cathode, there is a need for an ultra violet lamp. Furthermore, the wave length of ultra violet light is limited to about 0.1 micrometers (μm), and thus, duplication lithography below 0.1 micrometers is very difficult, if not impossible. Additionally, the lifetime of the photo electron plane is limited to a duplication cycle of approximately 50 cycles when using CsI for the photo electron plane. Moreover, although the quartz substrate 41 is quite conductive to ultra violet light, quartz is a relatively expensive material especially in large areas.
Furthermore, it is difficult to achieve a duplication that is precisely one-to-one between the pattern to be duplicated and the pattern that is created, without molding the surface of the photo cathode pattern 43 to be concave, which will result in surface roughness on the concave surface and a duplication that is even still difficult to produce in a one-by-one manner.